Objective: To compare the pregnancy rates and multiple pregnancy rates of cycles initiated in 1998 and in 1999, during which 3 and 2 embryos were advised to be replaced, respectively.
Study design: A retrospective study
Results: There were no differences between 1998 and 1999 in the pregnancy rate per cycle started or per transfer, implantation rate and the multiple pregnancy rates, despite a significantly lower number of embryos replaced in 1999. A significantly higher implantation rate was found in cycles with frozen embryos than those without. Using logistic regression analysis, the chance of pregnancy was significantly improved only by the presence of frozen embryos in the fresh cycles with an odds ratio of 2.0 (95% confidence interval: 1.3-3.0) whereas the chance of multiple pregnancy was significantly increased by replacing 3 embryos instead of 2 (odds ratio: 2.1, 95% confidence interval: 1.1-4.2).
Conclusion: Patients should be advised to have 2 embryos replaced without jeopardizing the pregnancy rates in the fresh cycles. The risk of multiple pregnancy is significantly increased when 3 embryos are transferred instead of 2.